Along with piles of rubbish and debris, storms have washed up sea life that's not commonly found on beaches along the east coast.

After the storm, Seven Mile Beach at Lennox Head was a marine life wonderland.

Southern Cross University marine ecologist Daniel Bucher says many of the species that have washed up come from much deeper water than normal.

While walking on the beach, he found a perfectly intact fig shell.

Dr Bucher says it's the first time in his 30-year career that he's come across one in such good condition.

"This is one that gets me excited because I started marine biology as a shell collector," he says.

"It's dead... the animal is very large when it's fully expanded and it lives in the sediment as a predator."

It's also brought in white sea cucumbers - sausage shaped animals related to starfish and sea urchins - which live in deep water on the ocean floor.

"These are what we call deposit-feeders, so they wait for material to settle on the bottom in the sand, they've got five tentacles around their mouth and they just use those to scoop in the sand. They just eat sand, digest out the organic material and poo out little sausages of clean sand," Dr Bucher says.

"The other interesting thing is also at the other end they have what's called a respiratory tree off their hind-gut which means they breathe through their anus."

In some parts of the world, some species of cucumber are harvested and eaten.

Dr Bucher says black sea cucumbers are occasionally found on northern New South Wales beaches, but it's not common to see the white kind.

"This is where the sand has been churned up a little deeper than normal and dug up these ones that are lying buried."

Unusually rough seas caused by ex-tropical cyclone Oswald may have killed plenty of marine life beyond the low-tide mark, but Dr Bucher says these kinds of infrequent weather events can be good for the ecosystem.

"It frees up some spaces that would've been taken over by the most competitive, dominant animal.

"That provides opportunity for new animals, sometimes different animals to occupy that space. So it's part of the process that maintains the high biodiversity of this region."